Linde H 50 D, Service Training

Page: 263 / 282

Service Training
Section 4.9
Page 37
12.05
OPERATION OF THE VAPORISOR
The LPG must be moved in gaseous form to process it with the intake air in the mixer as a flammable
mixture.
This is achieved by means of the vaporisor, which is heated by the engine cooling water.
It works as follows:
The IMPCO vaporisor is a combined two-stage regulator with vaporisor. It receives the LPG at tank
pressure from the vacuum-controlled shutoff valve with cleaning filter, and lowers this pressure in two
stages to a little less than atmospheric pressure (low pressure).
In the “off” position (engine off), the primary valve (2) is open and the secondary valve (10) is closed. The
secondary valve (10) prevents the gas from flowing out when the engine is off. This is assisted by the
spring (7) under the actuating lever.
The primary valve (2) is controlled by the pressure in the vaporisor chamber (11), which acts on the primary
diaphragm (3). This pressure passes through the hole (14) in the chamber in front of the diaphragm.
The diaphragm (3) moves around the pivot (16) and thereby presses the valve (2) in its seat. The spring
(15) creates the counter-pressure. The back of the primary diaphragm (3) is linked to the atmospheric
pressure via the compensating hole (14).
The secondary valve (10) can be activated mechanically by the manual actuator (5) for a cold start .
With the motor running (throttle valve of mixer open), a vacuum is created in the gas conduct to the mixer,
and this vacuum opens the secondary valve (10), so that the LPG can flow through the open primary valve
(2) into the vaporisor. The secondary valve (10) is controlled by the secondary diaphragm (4).
Due to the lowering of the pressure of the LPG (c. 10 bar in the tank) to atmospheric pressure, the LPG
expands, which results in a temperature drop. To compensate for the cooling and accelerate the
evaporation, the vaporisor is heated. To this end, the cooling water is passed through the water chamber
(12) of the vaporisor. By setting the throttle valve (by the position of the drive pedal), the secondary
diaphragm (4) is adjusted up or down, whereby the opening of the secondary valve (10) is controlled.
If the vacuum is increased by a dirty air filter, this vacuum opposes the opening pressure of the secondary
diaphragm (4) via connection (8). As a result, the secondary valve (10) is partly closed, the gas flow will
be reduced and an excess density of gas in the mixture will be prevented.
When the engine stops, the vacuum rises at connection (8). The secondary valve (10) shuts completely.
No more gas can now flow to the mixer.